A surface plasmon resonance (SPR) waveguide sensor with indium antimonide (InSb) adopted for the sensing section is proposed in the terahertz region. We investigate the SPR response, showing an ability to detect a temperature change. It is found that the sensitivity is estimatedto be about 7.5 × 10−3 THz/K.Key Words : Terahertz wave, InSb, Surface plasmon resonance (SPR) sensor, FDTD method